N-Hydroxy-4-(4-chlorophenyl)thiazole-2(3H)-thione as a Photochemical Hydroxyl-radical Source: Photochemistry and Oxidative Damage of DNA (Strand Breaks) and 2′-Deoxyguanosine (8-oxodG Formation)¶
摘要:
On irradiation of N-hydroxythiazole-2(3H)-thione 3 at 300 nm, the photoproducts disulfide 4, bisthiazole 5 and thiazole 6 are formed. During this photolysis, hydroxyl radicals are released, which have been detected by spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), coupled with electron paramagnetic resonance spectroscopy. In the presence of supercoiled pBR322 DNA, irradiation of thiazolethione 3 induces strand breaks through the photogenerated hydroxyl-radicals, as confirmed by control experiment with the hydroxyl-radical scavenger isopropanol, Singlet oxygen appears not to be Involved, as attested by the lack of a D2O isotope effect. During the photoreaction of thiazolethione 3 in the presence of 2'-deoxyguanosine (dG), the latter is photooxidized (ca 10% conversion after 2 h of irradiation) to the 7,8-dihydro-8-oxo-2'-deoxyguanosine as the main oxidation product. The dG conversion levels off after complete consumption of thiazolethione 3 and is suppressed by the addition of the hydroxyl-radical scavenger 2,6-di-tert-butyleresol or DMPO, Since the photoproducts 4-6 are ineffective as sensitizers for the photooxidation of dG and DNA, the hydroxyl radicals released in the photolysis of thiazolethione 3 are the oxidizing species of DNA and dG, These results suggest that the thiazolethione 3 may serve as a novel and effective photochemical hydroxyl-radical source for photobiological studies.
Photoreactions of N-alkoxy-4-(p-chlorophenyl)thiazole-2(3H)-thiones with l-cysteine derivatives in aqueous solutions
作者:Jens Hartung、Rainer Kneuer、Kristina Špehar
DOI:10.1039/b101097m
日期:——
Photolysis of substituted N-alkoxythiazolethiones 1
in aqueous solvents furnishes alkoxyl radicals 2, which, upon
stereoselective 5-exo-trig cyclization, are trapped by water
soluble thiols (L-cysteine, L-cysteine ethyl ester,
or the reduced form of glutathione, GSH) to afford disubstituted
tetrahydrofurans 3 in synthetically useful yields and with satisfactory to
excellent diastereoselectivities.
inherent weakness of the N,O bond, leading to products of isomerization and rearrangement. In a third instance, methyl translocation from oxygen to sulfur occurred to furnish a heteroaromatic N-oxide at the expense of a cross conjugated π-system. Consistent X-ray crystallographic data sets served as a basis for electronic structure method assessment in order to model aspects relevant to structure and decomposition